We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M * > 2 × 10 10 M ⊙ ) the large amount of gas funnelled toward the centre is completely consumed by the starburst, while in lower-mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower-mass barred galaxies than it is in higher-mass ones. Even though unbarred galaxies funnelled less gas toward their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution.

To investigate the role of bars in the chemical evolution of isolated disc galaxies, we performed a series of 39 gas dynamical simulations of isolated barred and unbarred galaxies with various masses, initial gas fractions, and AGN feedback models. The presence of a bar drives a substantial amount of gas toward the central region of the galaxy. In the most massive galaxies, this results in a violent starburst, followed by a drop in star formation resulting from gas exhaustion. The time delay between Type Ia and Type II supernovae explosions means that barred galaxies experience a rapid increase in [O/H] in the central region, and a much more gradual increase in [Fe/H]. In unbarred galaxies, star formation proceeds at a slow and steady rate, and oxygen and iron are produced at steady rates which are similar except for a time offset. Comparing the abundance ratios in barred and unbarred galaxies with the same central stellar mass M * , we find in barred galaxies an enhancement of 0.07 dex in [O/H], 0.05 dex in [Fe/H], and 0.05 dex in [O/Fe]. The [O/H] enhancement is in excellent agreement with observations from the SDSS. The initial gas fraction has very little effect on the abundance ratios in barred and unbarred galaxies, unless the galaxies experience a starburst. We considered AGN-host galaxies located near the bottom of the AGN regime, M * 3 × 10 10 M ⊙ , where AGN feedback dominates over supernovae feedback. We found that the impact of AGN feedback on the central abundances is marginal.

This article describes a microparticle enhanced nephelometric immunoassay (Nephelia) applied to the quantification of the thymic peptide hormone thymulin. Nephelia uses antibody recognition by the antithymulin antiserum in a competitive reaction between free thymulin and thymulin bound to the microspheres. The binding between microsphere and thymulin is achieved with the aid of a protein carrier. The sensitivity of the competitive reaction varied with the protein carrier and the antiserum sample. The most efficient reaction was obtained with the thymulin-metallothionein-microsphere conjugates; as little as 5 pg/ml of thymulin could be detected. In adult human serum or in its ultra-filtrate, spiked synthetic thymulin was totally recovered. Measurement of thymulin in serum or ultra-filtrate samples demonstrated the presence of interference from molecules in the serum. Nephelia led to the same conclusions as those reported with other methods and performs as well, and is more simple to use than radio- or enzymo-immunoassays for thymulin measurement.

No abstract